“…Condensation of chlorine and 3 leads to the formation of the corresponding polymer 4 , and further treatment with chlorine in acetic acid afforded the desired 1,2-bis-sulfinyl chloride 5 in good yield (Scheme ). The bis-sulfinates were obtained by condensation of ethane-1,2-bis-sulfinyl chloride and a chiral alcohol in the presence of pyridine (Scheme ), and the results are presented in Table . 2 Synthesis of Ethane 1,2-Bis-sulfinyl Chloride 3 Enantioselective Dynamic Kinetic Resolution of Ethane-1,2-Bis-sulfinyl Chloride 5 …”
Two modular and highly convergent approaches for the synthesis of both isomers of a large number of optically pure C(2)-symmetric bis-sulfoxides have been developed, and their scope and limitations have been assessed. The first one uses as intermediate diastereomerically pure C(2)-symmetric bis-sulfinate esters 6(S(S),S(S)) and 6(R(S),R(S)), obtained by dynamic kinetic resolution of ethane-1,2-bis-sulfinyl chloride 5. A single inducer of chirality, the glucose-derived DAG (diacetone-D-glucose) 1 is used for the enantioselective synthesis of both diastereomerically pure C(2)-symmetric bis-sulfinate esters, thanks to the opposite stereodirecting effect of pyridine and (i)Pr(2)NEt used to catalyze the reaction. The second approach is based on the copper-catalyzed oxidative coupling of optically pure lithiomethyl sulfoxides. Both isomers of a large number of methyl sulfoxides can be obtained in a convergent manner using (R(S))- and (S(S))-DAG methanesulfinate esters 8R(S) and 8S(S). Methanesulfinates 8R(S) and 8S(S) are also obtained in an enantioselective way by a dynamic kinetic resolution of methane sulfinyl chloride 24. The final bis-sulfoxides are obtained with enhanced enantioselectivities compared to the corresponding monomers, as a result of the Horeau effect which is operating in both approaches. A model based on the formation of pentacoordinated sulfur intermediate is proposed. This model can explain the dynamic kinetic resolution observed via Berry pseudorotations, without the commonly accepted in situ racemization of the starting material. The usefulness of the approaches is demonstrated by the preparation of complexes of Pd(II) and Ru(II) bearing bidentated chiral sulfoxides as ligands.
“…Condensation of chlorine and 3 leads to the formation of the corresponding polymer 4 , and further treatment with chlorine in acetic acid afforded the desired 1,2-bis-sulfinyl chloride 5 in good yield (Scheme ). The bis-sulfinates were obtained by condensation of ethane-1,2-bis-sulfinyl chloride and a chiral alcohol in the presence of pyridine (Scheme ), and the results are presented in Table . 2 Synthesis of Ethane 1,2-Bis-sulfinyl Chloride 3 Enantioselective Dynamic Kinetic Resolution of Ethane-1,2-Bis-sulfinyl Chloride 5 …”
Two modular and highly convergent approaches for the synthesis of both isomers of a large number of optically pure C(2)-symmetric bis-sulfoxides have been developed, and their scope and limitations have been assessed. The first one uses as intermediate diastereomerically pure C(2)-symmetric bis-sulfinate esters 6(S(S),S(S)) and 6(R(S),R(S)), obtained by dynamic kinetic resolution of ethane-1,2-bis-sulfinyl chloride 5. A single inducer of chirality, the glucose-derived DAG (diacetone-D-glucose) 1 is used for the enantioselective synthesis of both diastereomerically pure C(2)-symmetric bis-sulfinate esters, thanks to the opposite stereodirecting effect of pyridine and (i)Pr(2)NEt used to catalyze the reaction. The second approach is based on the copper-catalyzed oxidative coupling of optically pure lithiomethyl sulfoxides. Both isomers of a large number of methyl sulfoxides can be obtained in a convergent manner using (R(S))- and (S(S))-DAG methanesulfinate esters 8R(S) and 8S(S). Methanesulfinates 8R(S) and 8S(S) are also obtained in an enantioselective way by a dynamic kinetic resolution of methane sulfinyl chloride 24. The final bis-sulfoxides are obtained with enhanced enantioselectivities compared to the corresponding monomers, as a result of the Horeau effect which is operating in both approaches. A model based on the formation of pentacoordinated sulfur intermediate is proposed. This model can explain the dynamic kinetic resolution observed via Berry pseudorotations, without the commonly accepted in situ racemization of the starting material. The usefulness of the approaches is demonstrated by the preparation of complexes of Pd(II) and Ru(II) bearing bidentated chiral sulfoxides as ligands.
“…So far, various secondary carbinols, chiral amides, and sultam have been used to generate diastereomerically pure acyclic sulfinylating transfer reagents by either kinetic or dynamic transformation of sulfinyl chlorides. It is worth mentioning that actually a large number of methods permit the synthesis of diverse kind of alkyl, aryl, and functionalized sulfinyl chlorides (Scheme ), broadening the scope of these approaches. − 38 …”
Section: Nucleophilic Substitution On Chiral Acyclic
Sulfinylating Tr...mentioning
Recently, Keinan and Nimri reported an interesting antibody-metalloporphyrin that mimics natural oxidation enzyme. 105 On the basis of the catalytic Scheme 14 Scheme 15 Scheme 16
“…Certainly, these derivatives differ in terms of chemical and configurational stability. Sulfinyl chlorides have been mainly prepared as reactive intermediates without bothering about enantiomeric purity, and their storage is problematic (a contact with moisture evolves gaseous HCl). − Sulfinic acids are prone to disproportionation, yielding diaryl thiosulfinates and sulfonic acids . Stability of sulfinyl derivatives was extensively studied by Kice and co-workers.…”
Section: Chiral
Organic Compounds With a Tetrahedral
Sulfur Stereocentermentioning
Chiral sulfinyl compounds,
sulfoxides, sulfoximines, sulfinamides,
and other derivatives, play an important role in asymmetric synthesis
as versatile auxiliaries, ligands, and catalysts. They are also recognized
as pharmacophores found in already marketed and well-sold drugs (e.g.,
esomeprazole) and used in drug design. This review is devoted to the
modern methods of preparation of sulfinyl derivatives in enantiopure
or enantiomerically enriched form. Selected new approaches leading
to racemic products for which the asymmetric variant can be developed
in the future are mentioned as well.
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